Fluid pressure operated switch



Oct. 16, 1951 w, H, RUFFLE 2,571,617

FLUID PRESSURE OPERATED SWITCH Filed July 23, 1949 l /V m i j .E /f 26 f6 5 7 /7/9 6L www; g 5E/72 5)" www, A uw y ce.

Patented Oct. 116,719.51'

UNITED STATES PATENT OFFICE William Harry Ruffle, Hove, England, assignor to Speed Development Company Limited, Hove,

England Application July 23, 1949, Serial No. 106,383 In Great Britain July 30, 1948 Claims.

This invention relates to uid pressure operated switches adapted to respond to the inuence of hydraulic or gaseous fluid pressure for making and/or breaking a circuit for apparatus actuated electrically, or for bringing into and out of circuit an electrically operated controller or other apparatus.

An object of the present invention is to provide a very sensitive and resilient switch which will respond to very small changes in pressure, in which a diaphragm is exposed to the pressure fluid which, e. g. can have an effective operative pressure as low as 0.5 inch W. G., and having means preventing overloading of the diaphragm so that it can be very thin and highly sensitive, so that, by way of example, the present switch is suitable for operating a stall warning signal on aircraft, that is to say, it will respond effectively to pressure obtained as a signal of the immediate approach of the stalling speed of an aeroplane.

Another object of the invention is to provide a highly sensitive fluid pressure operated switch in which a switch element resiliently loaded against the fluid pressure actuating the diaphragm will not transfer the load of the resilient means to the diaphragm otherwise than as a yielding load when the diaphragm is deformed by fluid pressure to displace a driver member operatively engaged with the said switch element.

A further object of the invention is to provide a switch in which the above-mentioned resiliently loaded switch member is loaded by a weight to counteract the effect of the weight of a driver member actuated by the deformations of the diaphragm and engaged operatively with said resiliently loaded switch member, so that the switch is not affected by changes from the normal travelling position of balance or poise of the craft.

A still further object of the invention is to provide means whereby very fine adjustments may be effected readily to the effective pressure or load opposing actuation of the switch by the fluid pressure.

Still further objects of the present invention will be apparent hereinafter when reference is made to the accompanying drawings illustrating Aan embodiment of the invention, and wherein,

Figure 1 is a sectional elevation of the switch. Figure 2 is a section on the line II-II of Figure 1.

Figure 3 is a section on the line III-III of Figure 2, and

Figure 4 is an inverted plan view of a spring element of the switch.

Referring to the drawings the switch mechanism is housed within a cover cap I and an angle section base ring 2 threaded to the cap I as at 3 to grip in position a cylindrical base plug 4 and a disc 5 together with a sealing ring 6. Gripped between the opposed faces of the plug 4 and disc 5 is a flexible diaphragm 1, which, within the outer annular part gripped between the aforesaid members 4 and 5 is exposed for deformation by fluid pressure to a shallow concentric recess B in the plug 4, this recess 8 communicating via a passage 9 with a source of fluid pressure, and for this purpose a union I0 can be fitted in the plug 4 for connection by a suitable conduit to the source of fluid pressure. On the other side the diaphragm extends across a Very shallow concentric recess II in the base of the disc 5, this recess I I surrounding by a slight clearance a concentric shallow compartment I2 accommodating the disc-like head I3 of a stud I4 slidable through the centre of the disc 5. The flange I5 on the upper part of the stud I4, which rests upon the upper face of the disc 5 when there is no pressure upon the lower side of the diaphragm l, prevents actual physical contact of the disc I4 against the diaphragm 'I, or at most permits only light touch contact. The arrangement in any event being such that the deformation of the diaphragm due to fluid pressure will have to be exceedingly slight in order to ensure effective engagement between the diaphragm and the disc-like head I3 of the stud.

Also, the periphery of the disc-like head I3 has a quite narrow operative clearance from the cylindrical wall of the recess I2, so that there will be no deformation of the diaphragm otherwise than that which is effective upon the base of the disc-like head I3, excepting for the very narrow intermediate annular part of the diaphragm between its sealed outer annular part and the periphery of the disc-like head I3, this intermediate part merging smoothly into the central stud head engaging part. This manner of supporting the stud I4 with its head I3 ensures a highly sensitive response to the action of the diaphragm and relieves the diaphragm from harmful strain due to Very heavy fluid pressure, so that the switch whilst being exceptionally sensitive can be employed in recording a drop in pressure in a circuit or container subjected to a very high fluid pressure. Likewise the plunger I5 acts as a positive stop preventing harmful deformation of the diaphragm by the spring means, hereinafter described, which yieldingly opposes the action of the iiuid pressure against the diaphragm. However, as previously indicated the switch of the present invention is adapted to be sensitive and highly responsive to a wide range of Variations in pressures. For example, the pressure on the diaphragm which would maintain the stud I4 raised may be air pressure due to the speed of aircraft, so that when the pressure drops below a predetermined point a signal can be produced indicating that the aircraft is dangerously approaching the stalling speed of the aircraft.

The top of the stud I4 isv brought to spherical form as shown to make point contact with a switch lever I6 fulcrumed on a pivot pin I1 secured at its ends in a pair of blocks I8 fixed to the disc by studs I9. This lever I6 is a metal plate of substantially T configuration the centre limb part of which carries at its free extremity a resilient blade 2-0 having platinum or other suitable contacts 2| adapted'to engage platinum .or Yother suitable contacts 22 carried by a blade .1,23 secured to an insulator bridge 24 by a terminal screw 25 to which a lead 26 is taken to the appropriate part of the circuit of a warning or other 'suitable electrically operated device. The Yother electrical connection is taken off the switch by a lead 27 connected to a part of the Switch mechanism hereinafter described which 'will form electrical connection with the lever 28 and `which embodies means -for varying the effective Apressure of a leaf spring 28 -upon the lever I6 Vbetween the fulcrum II and the contact carrier blade 23.

VTheleaf'spring V28 together Ywith another spring hereinafter' described, yieldingly opposes the influence of the huid pressure upon the stud I4 so'that when the fluid pressure drops below a Vpredetermined load the leaf spring 23 will bring the'contacts 2l and 22 into engagement.

The object of making the switch lever i5 T shapeyis toprovide aneasily standardised methvod of weighting the lever at one end, but of course other means can be adopted for this purpose.

:It will'be seen by reference to VFigure l, which .for the purpose of explanation might be regarded as the normal or upright position of the switch, that`the transverse limb i6' assists in .the Alift or off movement o'f the lever I6, but in the event of the switch being turned upside down 'the counter-weight forming part I5 by reason of carefully predetermining its mass will neutralise the effect Vof the weight of the stud I and its flange I3 upon the lever I6.

The leaf spring 28 is downwardly bowed or cranked at its free end 29 to engage the lever I6 and at its other end is secured to one end of a block 30 fixed to the disc 5, the upper face of this block 30 being formed with aslight taper as indicated at 3I in Figure 3, thus providing a yprogressively changing narrow clearance between the lower face of the leaf spring and the upper face of the block 30. The adjustment of the effective load of the leaf spring upon the lever I5 is obtained bytranslating across the upper face of the leaf spring a square nut 32 having a bevelled lower edge 33 providing a line or chisel point contact with the spring. This nut is translated lengthwise of the spring by the rotation of va feed screw 34 guided between the opposed parallel sides of an oblong frame'35, pivoted at Ione lend by a pin`36 engaged at its ends in the ver- Aticallimbs of an inverted U.shaped post 31. 'One end of the screw y3l! is journalled Yin .the

pivoted end of the frame 35 and is provided with a square bore 38 for the reception of a tool for rotating the screw, the other end of the screw being supported by a reduced diameter portion 3S in a bush 40 threaded into the free end of the frame 35. Hence by careful adjustment of the bush ,40 the screw 34 is held against axial displacement and is rmly supported for rotation thus ensuring extreme accuracy in the translative adjustment of the nut 32 for varying the effective length of the leaf spring 28.

The object of the leaf spring 28 is to provide for very fine adjustment of the effective pressure opposing the fluid pressure, and such adjustment is additive to the constant pressure of a leaf spring 4I upon the free end of the frame 35, one end of this leaf spring I being secured to the upper portion of the inverted U-shaped post 3'! by a clamping bar 42 secured to the post 31 by studs 43.

If `desired the interior of the cap vhousing Amember I Vcan be fitted with a union 44 for the admission of static kpressure to Ythe interior of the housing, e. g. as when employing the device in conjunction with Va Pitot tube or equivalent vdevice upon aircraft.

It will be appreciated that the slight incline `or bevel `3| given to the blocks 30 will assist in thefirm support of the leaf spring 28 whilstpermitting of a gradual deformation of such spring without imposing undesirable loads on the spring.

I claim: Y

1. A fluid pressureoperated switch comprising `a base structure, a fluid pressure receiving compartment, a fluid pressure inlet to said compartment, an imperforated diaphragm sealed completely around its periphery and disposed across Vsaid compartment-so that only one side thereof is subjected to the direct impact of the fluid pressure from said inlet, a stud coeaxialwith the diaphragm and slidable through the base structure, a disc-like head on'said stud opposed to but free of said diaphragm so as to be engaged by the diaphragm when the latter is deformed by the Vfluid pressure soas to urge the stud in the direction of deformation of the diaphragm, a very shallow compartment accommodating said disc-like head with avery narrow clearance from the periphery of said head opening into and concentric with and very ynarrowly axially spaced from the saidxiiuid pressure receiving compartment so that thesaid head and the'ambient part of the wall-ofthe fluid pressure receiving compartment only permit of a very limitedy deformation of the diaphragm irrespective of the head offiluid pressure, an abutment on said Ystud which rests upon the .base structure to relieve the diaphragm of pressurevia Ythe stud and its head when the diaphragmis not pressing against saidhead, alereroperatedinone direction .and engaged by said stud, contacts brought into and out of engagement by the movement of said lever, spring means yieldinglyopposing the displacement of the 'lever by the actionof the fluid pressure, and means neutralisingV the Yinfluence ofthe weight of said switch actuating -weightedin :a `direction such that when the-.said

switch occupies a position in whichthegswitch actuating stud will supplement any load due to fluid pressure upon the diaphragm the weight of the stud is neutralised.

4. A switch according to claim l wherein said lever arm is a metal strip with a contact moving part at one end and fulcrumed between its ends, its other end being subjected to said neutralising load, the said strip being engaged between its fulcrum and its contact moving part with the said stud, adjustable spring means urging the said strip into engagement with the said stud.

5. A fluid pressure operated switch according to claim 4, wherein the spring means loading the lever comprises a leaf spring supported at one end and free at its lever engaging end, said leaf spring' being engaged by a relatively translatable abutment loaded against the leaf spring and manually controllable for varying its point of engagement with the leaf spring between the ends of the leaf spring to vary the effective load of the spring upon the said lever.

6. A fluid pressure actuated switch according to claim 5 wherein said abutment is a nut threaded upon a feed screw rotatable in a support shaped to guide the nut along the screw, said support for the feed screw being pivoted at one end and engaged at its other end by the said additional spring, whereby the said additional spring urges the said nut downwards against the said leaf spring engaging the switch member or lever.

7. A fluid pressure operated switch according to claim 6 wherein the leaf spring engaging the said lever extends for a portion of its length along a body member having an inclined surf ce opn posed to the said spring whereby a shallow clearance is afforded for the deformation of the spring.

8. A fluid pressure operated switch comprising a switch body, a compartment in said body, an inlet to connect said compartment to the source of fluid pressure, a fixed contact, a switch contact lever adapted to engage said fixed contact, a diaphragm sealed off at its periphery across said compartment so as to be exposed on one face to the fluid pressure, a driver member engaged by the face of the diaphragm remote from the face receiving the fiuid pressure and adapted to actuate said lever in one direction, spring means yieldingly opposing the displacement of the lever by the action of the uid pressure, means neutralising the influence of the weight of said switch actuating member against the switch lever, positive stop means preventing overloading of the diaphragm by the spring means yieldingly opposing the action of the fluid pressure upon the diaphragm, and also positive stop means preventing overloading of the diaphragm by the action of the fluid pressure and further spring means additionally loading said spring means adjustably loading the lever, said further spring means having in itself a substantially fixed effective load upon the switch member o1' lever.

9. A fluid pressure operated differential switch comprising a switch base body, a housing sealed to said base body, a compartment in said body, an inlet to connect said compartment to a source of fluid pressure, an inlet in said housing to connect the interior of the housing to another source of fluid pressure to obtain a. differential action, a fixed contact inside said housing, a lever arm inside said housing and pivoted between its ends, a contact on one end of said lever arm to engage said fixed contact, an imperforated diaphragm sealed off at its periphery across said compart ment so as to be exposed on one face to the fiuid pressure, a second compartment located in said base and exposed to the face of the diaphragm remote from the rst mentioned compartment, a disc loose in said compartment with its periphery nearly contacting the surrounding wall of said second compartment, a driver member x'ed to the centre of said disc and passing freely through the said base body and engaging the said lever, said driver member suspending said disc so that the disc is close to but applies no load to the diaphragm when the diaphragm is in its undeformed condition to obtain actuation of the said lever arm by fluid pressure applied to the diaphragm with very little deformation of the diaphragm, spring means yieldingly opposing the displacement of the lever by the action of the fiuid pressure against the diaphragm, and means neutralising the influence of the weight of said switch actuating member against the switch lever.

10. A fluid pressure operated switch responsive to very low operative pressures, i. e. as low as 0.5 inch W. G., comprising a housing, a base to which the housing is sealed, switch mechanism within the housing, means to connect the interior of the housing to a source of uid pressure, a diaphragm sealed at its perimeter in the base of the housing and exposed on one side to receive the influence of fiuid pressure from another source, a switch actuating stud slidable through said base, a disc head on said stud, a compartment containing and closely surrounding the periphery of said disc head, the other side of the diaphragm being disposed in close proximity to said disc head to actuate the switch when the diaphragm is deformed against said disc head by iuid pressure, said stud transmitting the displacement of the diaphragm due to fluid pressure to the said switch mechanism, a switch lever arm pivotally supported in the housing, spring means loading said lever arm so as to yieldingly oppose the fluid pressure upon the diaphragm, contacts made and opened by movement of said lever arm, an abutment on said stud engaging said base to prevent the load of said spring means being transferred to the diaphragm when the diaphragm is not deformed by fluid pressure, means to effect fine adjustments of the effective load of said spring means against said lever arm, and means additionally loading said lever arm in a direction which neutralises the influence of the weight of the said stud and disc head upon the said lever arm when the switch unit occupies a position such that the weight of the stud and disc head supplements the load due to the fluid pressure on the said switch member.

WILLIAM HARRY RUFFLE.

Ciran The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,117,213 Rodanet May l0, 1938 2,357,878 Crew Sept. l2, 1944 2,362,869 Wade Nov. 14, 1944 2,438,512 Mehut Mar. 30, 1948 2,499,040 Steinback Feb. 28, 1950 

